Smoke detector



FIG. 1 is a perspective view of the design for a smoke detector;

FIG. 2 is a top plan view of the design shown in FIG. 1;

FIG. 3 is a bottom plan view of the design shown in FIG. 1;

FIG. 4 is a front elevational view of the design shown in FIG. 1, the rear being identical; and

FIG. 5 is a side elevational view of the design shown in FIG. 1. 

The ornamental design for a smoke detector, as shown and described. 